I'm looking for texture/material anything with shell.
Sea shell?... nut shell? Do you have an image of the material you're after? Both of these possible types vary greatly...
Please try downloading the rmtl file by right clicking over the link and choosing "save link as". This works for me but I will try and determine why the link crashes the browser when clicked directly.
Your two examples are more complicated than what I did. I think the logarithmic spiral one might be fairly simple if the surface geometry also followed that curve. I'll try and mock up what I mean and post it for you.